The present invention relates to indicator lights for motor vehicles.
There is currently an increasing preoccupation with the production of an indicator light which, when it is illuminated, exhibits an illuminating surface which is as uniform is possible, and does so for any observation position in the luminous field of the lamp.
The deficiencies of known indicator lights equipped with a single source (filament-type lamp) interacting with a rear recuperator mirror are an excess of light intensity in that region of the bezel which is situated in line with the lamp, and which is exposed to the greatest density of luminous flux. When optical configurations of the Fresnel lens type are used, in combination with the lamp, the same kind of problem is encountered, the central region of the lens emitting a flux density which is appreciably greater than its peripheral region.
There is also known, from the document FR-A-2 614 969 in the name of the Applicant, an indicator light which is designed to offer a relatively uniform luminous intensity of its illuminating surface, over a substantial width but over a limited height (elongate light). To this end it includes a filament-type lamp interacting with a cup for angular distribution of the light, which surrounds it closely, and an optical straightening plate reflecting the radiation received from the cup substantially into the axis of the light.
However, this known light does not completely solve the problem of the lack of uniformity, in the sense that the arrangements for straightening the light which are provided on the plate exhibit coefficients of transmission of the light which vary greatly from one place to another, and in particular according to the amount of straightening demanded, such that, ultimately, such a light retains an appreciably greater density of luminous flux in line with the lamp than towards the lateral edges of the lamp.
Furthermore, the teachings of this document apply in a limited away to a light of restricted height, and give no indication making it possible to deal with the case of a light the illuminating surface of which exhibits not only a substantial width but also a substantial height.
An object of the present invention is remedy these limitations of the state of the art.
According to a first aspect of the invention, an indicator light for a motor vehicle comprises a light source, an optical plate possessing optical configurations adapted to straighten out the light originating from the region of the source so that it is propagated with an average direction generally parallel to a horizontal optical axis, and a flux-distributing and recuperating cup interposed between the source and the optical plate and adapted to provide a given distribution of the light over the inner surface of the optical plate in at least one given direction, characterized in that the optical plate has a height and a width of the same order of magnitude and possesses optical configurations exhibiting coefficients of transmission of the light which are different from one another, and in that the cup provides a given distribution of the light, both in the horizontal direction and in the vertical direction, which takes account of said different transmission coefficients so as to obtain an illumination at the exit from said plate which is essentially constant in the horizontal direction as well as in the vertical direction.
Preferred, but not limiting, aspects of the indicator light according to the invention are as follows:
said optical configurations possess transmission coefficients which change in steps as a function of their position along at least one of the horizontal and vertical directions, and the given distribution of the light by the cup also changes in steps along said direction;
in at least one area of said plate and along at least one direction, the transmission coefficients of the optical configurations vary progressively, and the given distribution of the light by the cup in the direction of this same area is also progressive;
one of the faces of the cup is able to provide the desired distribution of the light in one of the horizontal and vertical directions, and the other face of the cup is able to provide the desired distribution of the light in the other direction;
the outer face of the cup is able to provide the desired distribution of the light in the direction corresponding to the larger dimension of the optical plate;
said outer face of the cup possesses a plurality of striations;
the inner face of the cup is essentially smooth;
the light source is a filament which is elongate along a direction corresponding to the smaller dimension of the optical plate; and
the optical configurations of the optical plate are constituted by individual deflecting blocks operating either by refraction or by internal reflection.
According to a second aspect of the invention, there is provided a method of manufacturing a motor-vehicle indicator light, said light comprising a light source, an optical plate exhibiting horizontal and vertical dimensions of the same order of magnitude, and possessing first optical configurations adapted to straighten out the light originating from the region of the source so that it is propagated with an average direction generally parallel to a horizontal optical axis, said first optical configurations possessing different coefficients of transmission of the light, as well as a flux distributing and recuperating cup interposed between the source and the optical plate and including second optical configurations able to provide a given distribution of the light over the inner surface of the optical plate in the horizontal and vertical directions, characterized in that said method comprises the following stages:
establishing a law of change of the transmission coefficients of said optical configurations as a function of the horizontal and vertical coordinates of these optical configurations on the plate;
establishing, on the basis of said law, a relationship between the orientation of a ray originating from the source and incident on said second optical configurations and said horizontal and vertical coordinates, in such a way that the combination between said law and said relationship provides an essentially constant illumination at the exit from the plate along the horizontal and vertical directions;
defining the geometry of said second optical configurations as a function of said relationship;
manufacturing a mould for said cup by using said geometry; and
molding the cup with the aid of said mould.
Preferred, but not limiting, aspects of the method of the invention are as follows:
the stage of establishing a relationship is carried out while also taking account of an indicatrix of emission from the source in the direction in question;
the stage of establishing a relationship is carried out while also taking into account a transmission coefficient of said second configurations;
the definition stage consists in successively defining, over at least one of the faces of the cup, a plurality of second adjacent optical configurations as a function of the laws of refraction and/or of total reflection;
the definition stage consists in defining, over at least one of the faces of the cup, a smooth surface forming second optical configurations in the continuity of one another as a function of the laws of refraction; and
the definition stage comprises two separate and independent sub-stages applied respectively to the two faces of the cup and corresponding respectively to the horizontal direction and to the vertical direction.
Other aspects, aims and advantages of the present invention will be apparent on reading the following detailed description of a preferred embodiment thereof, given by way of non-limiting example.